const lan_china = function(){
    this.write =function(){
        console.log("我会说中文");
    }
}
const lan_add = function(obj){
    let oldwrite = obj.write;
    return {
        oldwrite ,
        newwrite : function(){
             console.log("我会说英文了");
        }
    }
}

var lan = new lan_china()
var new_obj = lan_add(lan)
new_obj.oldwrite();
new_obj.newwrite();